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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Use</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="ext_concurrency.html" title="Chapter 29. Concurrency" /><link rel="prev" href="ext_concurrency_impl.html" title="Implementation" /><link rel="next" href="appendix.html" title="Part IV.  Appendices" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Use</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_concurrency_impl.html">Prev</a> </td><th width="60%" align="center">Chapter 29. Concurrency</th><td width="20%" align="right"> <a accesskey="n" href="appendix.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.use"></a>Use</h2></div></div></div><p>Typical usage of the last two constructs is demonstrated as follows:
</p><pre class="programlisting">
#include &lt;ext/concurrence.h&gt;

namespace
{
  __gnu_cxx::__mutex safe_base_mutex;
} // anonymous namespace

namespace other
{
  void
  foo()
  {
    __gnu_cxx::__scoped_lock sentry(safe_base_mutex);
    for (int i = 0; i &lt; max;  ++i)
      {
	_Safe_iterator_base* __old = __iter;
	__iter = __iter-&lt;_M_next;
	__old-&lt;_M_detach_single();
      }
}
</pre><p>In this sample code, an anonymous namespace is used to keep
the <code class="code">__mutex</code> private to the compilation unit,
and <code class="code">__scoped_lock</code> is used to guard access to the critical
section within the for loop, locking the mutex on creation and freeing
the mutex as control moves out of this block.
</p><p>Several exception classes are used to keep track of
concurrence-related errors. These classes
are: <code class="code">__concurrence_lock_error</code>, <code class="code">__concurrence_unlock_error</code>, <code class="code">__concurrence_wait_error</code>,
and <code class="code">__concurrence_broadcast_error</code>.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_concurrency_impl.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_concurrency.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="appendix.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Implementation </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Part IV. 
  Appendices
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